1. Field of the Invention
This invention relates to storage systems. In particular, it relates to a power saving archive system.
2. Description of the Related Art
List of Patent References:    A. Nunnelley, Lewis L; Williams, Larry L; Wood, Jr, Leighton C: High Capacity Data Storage System using Disk Array. Issued Jun. 6, 1995: U.S. Pat. No. 5,423,046.    B. Winokur, Alex: Computer with Reduced Power Consumption. Issued Dec. 1, 1998: U.S. Pat. No. 5,845,291.    C. Smith, Gordon J: Adaptive Disk Drive Operation with Medium Speed and Recording Location based on Data Type. Issued Jun. 4, 2002: U.S. Pat. No. 6,400,892.    D. Hakamata, Kazuo; Takamoto, Kenichi; Kobayashi, Masaaki: Disk Array Unit. Issued Jun. 24, 2003: U.S. Pat. No. 6,583,947. Continuations: U.S. Pat. Nos. 6,826,005 and 6,947,240.    E. Halleck, Michael D: Apparatus and Method for Reducing Power Consumption in an Electronic Data Storage System. Issued Dec. 17, 2002: U.S. Pat. No. 6,496,915.    F. Kistler, Michael David; Rajamony, Ramakrishnan: Multiple Disk Data Storage System for Reducing Power Consumption. Issued Nov. 1, 2005: U.S. Pat. No. 6,961,815. Continuation: U.S. patent application publication number 20040111558.    G. Fisk, Ian; Mojaver, Michael: Lower Power Disk Array as a Replacement for Robotic Tape Storage. Filed Mar. 21, 2003. U.S. Patent application publication number 20040068672. Continuation: U.S. patent application publication number 20090119530.    H. Guha, Aloke; Santilli, Chris T; McMillian, Gary B: Method and Apparatus for Power-Efficient High-Capacity Scalable Storage System. Issued Apr. 25, 2006: U.S. Pat. No. 7,035,972. Continuations: U.S. Pat. No. 7,210,005; U.S. patent application publication numbers 20040054939, 20050268119, 20060129761, and 20070220316.    I. Amano, Takashi: Data Storage Systems and Methods. Filed Feb. 25, 2004. U.S. Patent application publication number 20050188252.    J. Kaiju, Yoshihiko; Yoshida, Shoichi; Murakawa, Yoshitaka; Futamata, Akio; Ito, Katsuyoshi: Power Saving Control System and Power Saving Control Method. Issued Sep. 25, 2007: U.S. Pat. No. 7,275,166. Continuation: U.S. patent application number 20050273638.    K. Oshikawa, Hiroshi; Saitoh, Hirofumi: Data Storage Device and Control Method for Power-Saving Modes of Serial Interface Thereof. Issued Jan. 6, 2009: U.S. Pat. No. 7,475,265.    L. Lubbers, Clark Edward; DeCenzo, David Peter: Power Management in a Storage Array. Filed Jun. 28, 2007. U.S. Patent application publication number 20090006877.
In the discussions to follow, patents and their continuation applications are referenced by their letters in the above list, and/or by their inventors or their numbers.
The majority of the above-referenced documents consists of disk arrays with a single master controller or CPU in communication with data storage users or hosts. This includes A, B, C, D, F, H, and K, and most of E, G and L. Such arrays include MAID systems (H), RAID-based systems (H, L), systems that organize files into clusters on selected disks (A, H), systems that cache data into semiconductor memory or flash memory (B, E), and even systems that work with the space between platters on a disk (C).
However, power saving on a disk level proves to have two drawbacks. First, not much power is saved. Typical MAID performance is 30% to 40% power saving, due to the continued demands of CPU, fan and other power users in the enclosure. They require a controller (G) for all the disks, quiescent or not.
Second, complexity tends to skyrocket as the size (measured in number of disks) moves beyond the capacity of one enclosure. This also results in latencies and trouble with data throughput.
Having to micro-manage data via involvement in RAID, cache, or file characteristics (C, F, J) is another drawback of many of the references. Powering down and up are major disturbances in data flow. If the same control mechanism that causes these massive effects must be involved in delicate details of a file system, there is built-in danger of instability and race conditions that can result in data corruption.
Micro-management is also a problem in K, as the host has to control the power saving function by explicit commands.